smear

nouns

slanderous defamation
a thin tissue or blood sample spread on a glass slide and stained for cytologic examination and diagnosis under a microscope
a blemish made by dirt
"he had a smudge on his cheek"
an act that brings discredit to the person who does it
"he made a huge blot on his copybook"

verbs

stain by smearing or daubing with a dirty substance
is a type of (narrower)
make soiled, filthy, or dirty
"don't soil your clothes when you play outside!"
make a smudge on; soil by smudging
cover (a surface) by smearing (a substance) over it
"smear the wall with paint"; "daub the ceiling with plaster"
charge falsely or with malicious intent; attack the good name and reputation of someone
"The journalists have defamed me!" "The article in the paper sullied my reputation"